Mold.



UNTTE STATES PATEN T @FFTCE S PACK, OF BROOKLYN, NEW YORK, ASSIGNOB TODQEHLER DIE CASTING 'CQMTANY, OF BROOKLYN, NEW YORK, A CORPORATIQN OFNEW YUM.

Patented Apr, 2% 11%19.

OH H e z morn.

ll,3ll,9afii5, Specification of Letters Patent.

No Drawing. I

T 0 all whom it may concern:

Be it known that l, CHARLES PACK, a citizen of the United States,residing at the borough of Brooklyn, in the city of New York, county ofKings, and State of New York, have invented certain new and usefulImprovements in Molds, of which the following is a specification. v

My invention relates to molds and more particularly to a type of moldmade of p1as tic material adapted to be used in the casting of fluid mtals.

Molds of the character to which my invention relates are used in theproduction of intricate castings requiring little or no machining afterbeing drawn from the mold and having sufliciently exact dimensions topermit them to'be incorporated in the diderent mechanisms withoutrequiring material machine work thereon. Castings made in such moldspossess all of the surface characteristi'cs of finished castingsproduced by what is known as the pressure die casting precise as toaccuracy of dimensions and Heretofore in the production of molds formaking such castings, it has been the practice to employ a mixturecomposed of the ordinary commercial plaster of Paris and owderedasbestos either with or without a "brous fusible binder for the purposeof securing greater tenacity in the body of the mold, or through theburning out of said fibrous material to form ducts to secure-a morerapid venting of the moldduring the pouringoperation' In making themolds the mixture is formed in suitable frames about patterns which maybe made of metal or of low fusing material such as wax. l have found inproducing molds of this char actor, there is a tendency of the plasticto imprison air in and about the surface of the pattern, particularlywhere sharp angles or depressions are presented in the pattern, thusnecessitating the agitation of the plastic mass about the pattern tofree any such imprisoned air and secure exactitude in the mold cavity.By experiment, l have discovered that the composition consisting ofasbestos and plaster of Paris is not suitable for the production ofmolds of this character because the mixture cannot be satisfactorilyhandled except when it has thickened or become partially set by reasonofthe tendency of water in excess of that required inform- Applicationfiled January 5, 1917. Serial No. 140,711.

ing a combination with the solids of the plastic material, to stratifyand come to the top of the mold.

Furthermore, it have found it necessary to use a composition which maybe poured into the frame in a fluid or viscous condition to permit theagitation thereof about the pattern in a manner to prevent the formationof bubbles or blow-holes upon'the surface of the cavity into which themetal is to be poured. With the asbestos and plaster of Pariscomposition, if the mass be sufliciently fluid to permit of itsagitation as above referred to, the water will not. only accumulate atthe top of the mold being formed in the manner above referred to, butthe plaster of Paris will be precipitated, forming a stratum at thebottom of the mold, the asbestos constituent forming a stratumintermediate the plaster of Paris and the water which stratum is tooweak to withstand the stresses incidental to the casting operation andwhich rapidly cracks in a manner to form fins upon the casting whichfins make the casting diflicult to remove, and necessitate complicatedmachine refinishing of the castings. Furthermore, the stratum of plasterat the bottom of the mold is very much less porous than the stratum ofasbestos and has a tendency to warp during the drying out of the moldprior to the casting operation. This condivtion also results in a mold,different portions With these conditions in mind, the object of myinvention is to provide a mold of plastic material, the nature of theingredt outs of which will be such as to have atlinity for each otherand have absorptive properties which will avoid the stratification ofexcess water and of the solid ingredients entering into the composition.

A mold made in accordance with my invention, when the composition sets,will have substantial homogeneity throughout the entire. body thereofand the patterns may be drawn therefrom in a manner to leave smoothsurfaces and sharp edges owing to the tenacity of the material of themold which will be sufficiently great to prevent the breaking orchipping of the material of the mold as a result of theforce applied inremoving the pattern; All parts of the mold will be suiiiciently porousto admit a free venting during the casting operation and the uniformporosity of all parts of the mold facilitates the elimination of themoisture in the mold by heat drying without likelihood of the warping ofthe mold due to the necessity for a prolonged subjection of the mold toheat, after any portion thereof has been thoroughly dried.

In the production of a mold made in accordance with my invention, theingredients I employ are such as to permit the pouring of the plaster,while in a fluid or viscous state, about the pattern or patterns andwithin a frame, and the subsequent agitation of'the plastic materialabout the pattern or patterns in a manner to expelthe air and thusinsure the smooth surfaces in the finished mold.

Furthermore, the composition of the mold makes possible the separationof enough of the moisture, either free or in combination with the solidscontained in the mold by a uniform application of heat withoutlikelihood of prematurely drying portions there of wlth a resultantwarping or distortion of the portions of the molds which are the firstto lose their moisture.

The invention consists primarily in a mold formed of plaster of Parisand a granular, porous, non-fibrous and absorptive material having anafiinity'for plaster of Paris; and in the novel steps and practlces inmaking said mold all as hereinafter set forth and described and moreparticularly pointed out in the claims hereto appended.

In the practice of my invention, ll form a mold consisting ofpulverulent silicious sinter, also called kieselguhr, and cellite, mixedwith ordinary commercial plaster of Paris and a suitable fluid such asordinary water in such proportions as to secure the desired condition ofthe mixture. In practice, I have found the most satisfactory results aresecured by using equal quantities by bulk of kieselguhr or cellite andplaster of Paris, uslng enough water to make the compositionsufficiently fluid to readily flow. I do not desire, however, to limitmyself to the exact proportlons stated, as the roportions may be varied.I have found that the kieselguhr or cellite has a stron afiinity for theplaster of Paris, and that t e solids entering Into the compositionabsorb and retain moisture far in excess of that which w ll enter intocombination therewith.

In making the molds, I mix the plaster of Paris and kieselguhr orcellite while dry and add thereto the desired volume of Water,thoroughly mixing the composition. The mixture is then poured into aframe having placed therein. one, or a number of patte and by reason. ofits fluidity, the composition flows freely about each of the patternsand throughout the frame. After being so poured, it will remain fluidfor a suficient time to permit the molder to agitate the plastic abouteach pattern in a manner to free any imprisoned air and cause the fluidcomposition to closely hug the pattern. The composition is then allowedto set and there after the patternis drawn therefrom. l have found thatin setting, a composition, such as l have described, does not stratifybut solidifies intoa substantially homogeneous mass of substantiallyuniform density or porosity, and that the material is sum- 'cientlytenacious to permit the drawing of the pattern while the moldingmaterial is still wet without providing any substantial draft in thepatterns to avoid a break down of the walls in or about the mold cavity.This tenacity in the mold is highly desirable where split molds areused, although a matter of secondary importance where fusible patternsare employed. The other characteristics of the mold are of equalimportance, however, irrespective of the type of mold made.

After the patterns have been drawn, the mold is subjected to the actionof heat for a sufficient time and at sufficiently high temperature tonot only remove thefree moisture, or the moisture in suspension, in themold but also that moisture which has combined with the solidingredients of the mold, thus avoiding likelihood of injury to the moldwhen the molten metal is poured thereinto. llhe casting or castings aredrawn from the mold by breaking the mold from about same after the havesolidified.

The absorptive propertles of the mold, result in uniformity in thedrying action throu b all parts of the mold, thus avoiding li elihood ofthe distortion or working of small parts of themold about the cavitytherein.

While the outside ofthe mold has a tendency to dry first, nevertheless,the properties above referred to will gradually bring moisture to thesurface. of the mold and this drying of the outside will not have atendency to injure the molds in any way.

The non-conductive properties of a mold made in accordance with myinvention prevent a too rapid chilling of the lighter portions of thecastings while the uniform porosity affords ample venting of the moldwithout the necessity for providing special vent openings.

A completed mold made in accordance with my invention is substantiallydevoid of 3d 1161' of MP I at Letters Patent is:--'

- i aoi eaa 1 it to work the composition in making the molds in a mannerto secure'exactitude in the formation and dimensions of the mold cavityby reason of the possibility of us the com position while in a'fluid orviscous'condition it without likelihood of Stratification of thedifl'erent ingredients when the mold sets. Furthermore, Mesel hr orcellite' or an equivalent silicious smter, possesses superior qualitiesin that it is granular, porous, men 7 to fibrous, absorptive andhas an'aity for the .plaster o characteristics it has a low specific gravityand is .hlciently bulky to be more-economical in use than jasbestosOP-Slmllfil material. v

p it is not my intention to t the invention-to theexact proportionsherein reie to nor to the exact manner of '1: the Mesel and the plasterof Paris, it 1 H apparent hat such proportions and the depa a the spiritand scope at the invention. Hag ,descri the invention what i claim asnew and'de'sire to 1.- At mold adapted for the production ot intricatermetal cast formed oi laster of Paris and a granular, porous, non-.brouaabsorptive material ha i a an :tii m at ny for plaster of Paris.the mateal oil said mold. being devoid of moisture d moisture normallycombined with the d el advantage. in the u f the v deity, 7

Paris. in addition to these se may be varied without thereof, the com'ositionol the mold being a substantiall omogeneous mass ofsubstantiallyuni orm density. 7 2. A mold adapted for the production ofintricate finishedfrnetal castings deed of laster otllaris and cellite,in a substantially omogeneous mass oi substantially uniiorinv 3. A moldadapted for the productionot intri te that metal cast formedot.

plaster otiParis. and a silicious sinter, the

material'olt saidm'oldbein'g devoid of tree moisture andmoisturefnormally combined to with the-solids thereol, in asubstantially homogeneous mass of substantially uniform vdensi y.

t. A mold adapted tor the production oi intricate ed metal cast formedof to plaster of Paris and a 'silicious sinter in substantially equalquantities of bulk, thematerial of said mold being devoid of treemoisture and moisture normally combined with the solids thereot' in asubstantially home to geneous'mass of substantially uniform densit Amoldxadapted tor the production at intricate shed metal castingsformed-oi laster of Paris and cellite in a substantially 7t omoneousmass, the material of said mold being substantiallyih'ee from treemoisture v and moisture normally combined was the solids thereot. 1

ln witness whereof-l1 hereunto my it a w ature in the presence of twosubscribing wtnesses, t. it.

onus men w .Wnt. i'tGnr.

till

28th day of December, with K i

